1. Field of the Invention
The present invention relates to a focus detection device.
2. Description of Related Art
A focus detection device in the known art detects the focusing condition achieved by a photographic optical system based upon a phase difference (often referred to as an image shift) manifested by a pair of images formed with a pair of focus detection light fluxes having passed through different areas of the photographic optical system. Such a focus detection device adopting the phase detection method is known to give varying focusing condition detection results in correspondence to different phase difference detection directions due to the field curvature manifesting at the photographic optical system (see Japanese Laid Open Patent Publication No. 2009-128843). In more specific terms, the phase difference detected along a straight line (tangential direction) radially extending from the optical axis of the photographic optical system does not match the phase difference detected along a direction (radial direction) orthogonally intersecting the tangential direction on a concentric circle centered on the optical axis.